Treatment for improved magnesium surface corrosion-resistance

ABSTRACT

A method, a composition and a method for making the composition for increasing the corrosion resistance of a magnesium or magnesium alloy surface is disclosed. The composition is a water/organic solution of one or more hydrolyzed silanes. By binding silane moieties to the magnesium surface, an anti-corrosion coating on a magnesium workpiece is produced. A complementary method, composition and method for preparing the composition for treating a metal surface to increase corrosion resistance is disclosed. The composition is an aqueous hydrogen fluoride solution with a non-ionic surfactant.

[0001] This application is a continuation of U.S. patent applicationSer. No. 10/179,241 filed Jun. 26 2002 which claims priority from U.S.Provisional Patent Application Ser. No. 60/301,147 filed Jun. 28, 2001.

FIELD OF THE INVENTION

[0002] The present invention is directed to the field of metal surfaceprotection and more particularly, to a surface treatment that increasespaintability and corrosion resistance of magnesium and magnesium alloysurfaces.

BACKGROUND OF THE INVENTION

[0003] The light weight and strength of magnesium and magnesium alloysmakes products fashioned therefrom highly desirable for use inmanufacturing critical components of, for example, high performanceaircraft, land vehicles and electronic devices.

[0004] One of the most significant disadvantages of magnesium andmagnesium alloys is corrosion. Exposure to the elements causes magnesiumand magnesium alloy surfaces to corrode quickly, corrosion that is bothunesthetic and reduces strength.

[0005] One strategy used to improve corrosion resistance of metalsurfaces is painting. As the surface is protected from contact withcorrosive agents, corrosion is prevented. However, many types of paintdo not bind well to magnesium and magnesium alloy surfaces.

[0006] Methods based on chemical oxidation of an outer metal layer usingchromate-solutions are known in the art as useful for treating magnesiumand magnesium alloy surfaces to increase paint adhesion, see for exampleU.S. Pat. No. 2,035,380 or U.S. Pat. No. 3,457,124. However the lowcorrosion-resistance of treated surfaces and environmentalunfriendliness of chromate solutions are definite disadvantages of thesemethods.

[0007] In PCT publication WO 99/02759 is described a method of providinga protective coating to a magnesium surface by polymerizing anelectrostatically deposited resin comprising a variety of functionalgroups.

[0008] Several methods of metal surface treatment using silane solutionshave been disclosed, see for example U.S. Pat. No. 5,292,549, U.S. Pat.No. 5,750,197, U.S. Pat. No. 5,759,629 and U.S. Pat. No. 6,106,901.Silane solutions are environmentally friendly and lend excellentcorrosion resistance to treated metal surfaces. Silane residues from thesolution bind to a treated metal surface preventing oxidation andforming a layer to which commonly-used polymers, such as paint, adhese,see U.S. Pat. No. 5,750,197. Although successfully applied to steel,aluminum, zinc and the respective alloys, magnesium and magnesium alloyshave not been successfully treated with silane solutions.

[0009] U.S. Pat. No. 5,433,976 teaches alkaline solutions for thetreatment of metal surfaces, the solutions including an inorganicsilicate, inorganic aluminate, a cross-linking agent, and a silane.However, U.S. Pat. No. 5,433,976 does not teach the use of this solutionfor treating magnesium.

[0010] Another strategy used to improve corrosion resistance of metalsurfaces is anodization, see for example U.S. Pat. No. 4,978,432, U.S.Pat. No. 4,978,432 and U.S. Pat. No. 5,264,113. In anodization, a metalsurface is electrochemically oxidized to form a protective layer.Although anodization of magnesium and magnesium alloys affordsprotection against corrosion, adhesion of paint to anodized magnesiumsurfaces is not sufficient. Further, as discussed in U.S. Pat. No.5,683,522, anodization often fails to form a protective layer on theentire surface of a complex workpiece.

[0011] It would be highly advantageous to have a method for treatingmagnesium or magnesium alloy surfaces so as to increase corrosionresistance beyond what is known in the art.

SUMMARY OF THE INVENTION

[0012] The present invention is of a method, a composition and a methodfor making the composition for increasing the corrosion resistance of amagnesium or magnesium alloy surface. The composition is a water/organicsolution of one or more hydrolyzed silanes. By binding silane moietiesto the magnesium surface, an anti-corrosion coating on a magnesiumworkpiece is produced.

[0013] According to the teachings of the present invention there isprovided a composition useful for treating of a magnesium or magnesiumalloy surface to increase polymer adhesion and corrosion resistance ofthe surface, the composition being a silane solution having a pH greaterthan about 4 and including at least one hydrolyzable silane in a watermiscible solvent.

[0014] The solvent is one or more materials chosen from amongst water,alcohols, acetone, ethers and ethyl acetate.

[0015] The silanes are one or more silanes having at least one nonhydrolyzable functiona; group chosen from amongst amino, vinyl, ureido,epoxy, mercapto, isocyanato, methacrylato, vinylbenzene and sulfanefunctional groups. Suitable silanes include, for example,vinyltrimethoxysilane, bis-triethoxysilylpropyl tetrasulfane,aminotrimethoxysilane, and ureidopropyltrimethoxysilane.

[0016] According to a feature of the present invention, the totalconcentration of hydrolyzable silanes in the silane solution ispreferably between about 0.1% and about 30%, more preferably betweenabout 0.5% and about 20% and even more preferably between about 1% andabout 5%.

[0017] There is also provided according to the teachings of the presentinvention a method of treating a magnesium or magnesium alloy surface bypreparing a silane treatment solution as described above and bring thesolution in contact with the surface.

[0018] According to a feature of the present invention, preparation ofthe silane solution includes hydrolyzing the silanes in an aqueoussolution having a pH of less than about 6, the pH achieved by addingacid, preferably acetic acid, to the hydrolyzing solution.

[0019] According to a feature of the present invention, preparation ofthe silane solution includes adding a base, preferably KOH, NaOH andNH₄OH, to the solution so that the final pH, subsequent to the additionof solvent, is at the desired value.

[0020] According to a feature of the present invention, when the treatedsurface is not anodized the pH of the silane solution is more than about6, preferably more than about 8.

[0021] According to a feature of the present invention, one solutionused to treat and anodized surface is where at least one of thehydrolyzable silanes in the silane solution is bis-triethoxysilylpropyltetrasulfane and the solution preferably has a pH of between about 5 andabout 8, more preferably of between about 6 and about 7. According to afeature of the present invention, when treating an anodized surface witha bis-triethoxysilylpropyl tetrasulfane solution, the totalconcentration of hydrolyzable silanes in the silane solution ispreferably between about 0.1% and about 5%, more preferably betweenabout 0.8% and about 2% and even more preferably between about 1% andabout 2%.

[0022] Alternatively, according to a feature of the present invention,when the treated surface is anodized, the silane solution can include atleast two different hydrolyzable silanes, the first being anonfunctional bisilyl (e.g. 1,2 bis-(triethoxysilyl) ethane,1,2-bis-(trimethoxysilyl) ethane, 1,6-bis-(trialkoxysilyl) hexanes and1,2-bis-(triethoxysilyl) ethylene,) and the second a vinylsilane (e.g.vinyltrimethoxysilane ). By “nonfunctional bisilyl” is meant thatexcepting the function that connects the two silicon atoms together, thefunctional groups of the silane are all hydrolyzable.

[0023] According to a feature of the present invention, when treating ananodized surface with a silane solution including two hydrolyzablesilanes the pH of the solution is preferably between about 4 and about7, more preferably between about 4 and about 5.

[0024] According to a feature of the present invention, when treating ananodized surface with a silane solution including two hydrolyzablesilanes the total concentration of hydrolyzable silanes in the silanesolution is preferably between about 0.1% and about 30%, more preferablybetween about 0.5% and about 20% and even more preferably between about1% and about 5%.

[0025] According to a feature of the present invention, when treating ananodized surface with a silane solution including two hydrolyzablesilanes the molar ratio of hydrolyzable nonfunctional bisilyl tohydrolyzable vinylsilane is preferably between about 50:50 and about10:90 and more preferably between about 20:80 and about 10:90.

[0026] According to a further feature of the present invention, prior tothe contact of the silane solution with the surface, the surface ispretreated, for example with a hydrogen fluoride solution.

[0027] According to a still further feature of the present invention,subsequent to the contact of the silane solution with the surface, apolymer such as paint, adhesive or rubber is applied to the surface.

[0028] There is also provided according to the teachings of the presentinvention an anti-corrosion coating having a layer including magnesiumatoms and silane moieties attached to at least some of said magnesiumatoms in said layer by Si—O—Mg bonds. According to a feature of thepresent invention, the anti-corrosion coating also includes fluorineatoms attached to at least some of said magnesium atoms in the layer.

[0029] There is also provided according to the teachings of the presentinvention a method of binding silanes moieties to a magnesium ormagnesium alloy surface by applying the silane solution as describedabove to the surface. Also provided according to the teachings of thepresent invention is a method of binding silanes moieties to an anodizedmagnesium or magnesium alloy surface by applying the silane solution asdescribed above to the surface, by first anodizing the surface in abasic anodizing solution.

[0030] There is also provided according to the teachings of the presentinvention an article having at least one magnesium-containing surfaceand a corrosion resistant coating, the coating including a plurality ofsilane moieties, the silane moieties bound to the magnesium-containingsurface by Si—O—Mg bonds. According to a feature of the presentinvention, at least about 1% of the plurality of silane moieties has atleast one functional group from a group consisting of amino, vinyl,ureido, epoxy, mercapto, isocyanato, methacrylato, vinylbenzene andsulfane.

[0031] The present invention is also of a method, complementary to themethod using silanes described hereinabove, a composition and method formaking the composition for treating a metal surface to increasecorrosion resistance. The composition is an aqueous hydrogen fluoridesolution with a non-ionic surfactant.

[0032] According to the teachings of the present invention there isprovided a composition (a treatment solution) useful for treating of ametal or metal alloy surface made up of hydrogen fluoride (HF) and anonionic surfactant in water. According to a feature of the presentinvention the composition has an HF content of between about 5% andabout 40%, by weight and a nonionic surfactant content of between about20 ppm and about 1000 ppm. According to a further feature of the presentinvention the nonionic surfactant is a polyoxyalkylene ether, preferablya poloxyethylene ether, preferably chosen from a group consisting ofpolyoxyethylene oleyl ethers, polyoxyethylene cetyl ethers,polyoxyethylene stearyl ethers, polyoxyethylene dodecyl ethers, such aspolyoxyethylene(10) oleyl ether.

[0033] There is also provided according to the teachings of the presentinvention a method of producing the treatment solution by combining theconstituent components.

[0034] Also provided according to the teachings of the present inventionis the treatment of a metal surface (corroded or not corroded) of aworkpiece with the treatment solution by contacting the surface with thetreatment solution.

[0035] Hereinfurther, the term “magnesium surface” will be understood tomean surfaces of magnesium metal or of magnesium-containing alloys.Magnesium alloys include but are not limited to alloys such as AM-50A,AM-60, AS-41, AZ-31, AZ-31B, AZ-61, AZ-63, AZ-80, AZ-81, AZ-91, AZ-91D,AZ-92, HK-31, HZ-32, EZ-33, M-1, QE-22, ZE-41,ZH-62, ZK-40ZK-51, ZK-60and ZK-61.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention is of a method and solution useful intreating magnesium surfaces, anodized or not, to produce acorrosion-resistant layer which is also useful for preparing a magnesiumsurface for painting. The principles and use of the method and solutionsof the present invention may be better understood with reference to theaccompanying description.

[0037] The ability of hydrolyzable silanes (for example, those havingone or more alkoxy or acyloxy substituents) to bind to metal surfaces iswell know to one skilled in the art. The binding of silanes with a metalsurface can generally be described as a three-step process. First, ahydrolyzable moiety is hydrolyzed. Second, the hydrolyzed silanemigrates to the surface of the metal where it binds to a hydroxy groupon the metal surface. Third and last, water is liberated and a covalentSi—O—Xx bond is formed, Xx being a metal atom.

[0038] Although there is some argument as to whether the silane layer isa monolayer or not, it is well known that the silane layer increases thecorrosion resistance of the metal surface to which it is bound. It isalso to known that when a metal surface is coated with a silane layerwhere the bound silane moieties have non-hydrolyzable organic functionalgroups, the layer increases adhesion of polymers such as paint,adhesives and other polymers. Apparently, the organic functional groupsof the silane effectively interact with various types of polymermolecules.

[0039] Silane layers have been successfully used to make a protectivecoating for metal surfaces such as aluminum or zinc. Unfortunately,magnesium surfaces have not been successfully treated with silanesolutions. The reasons arise from the virtually orthogonal requirementsof the magnesium surface on the one hand and of the silanes on theother.

[0040] Magnesium easily corrodes in acid and even slightly basicenvironments: magnesium surfaces do not corrode at pH 12, but at lowerpH corrosion does occur. Also, the concentration of the hydroxy moietyson a magnesium surface necessary for silane binding is related to pH. Atbasic pHs there is a high concentration of hydroxy moietys while atacidic pHs there is a dearth thereof.

[0041] In contrast, acidic environments are advantageous for binding ofmost silanes to metal. In general, the optimal pH for hydrolysis of mostsilanes is between 3 and 4. Further, in a basic environment, hydrolyzedsilanes often condense to form dimers and higher polymers. The additionof alcohols to a solution containing hydrolysed silanes is known toreduce the rate of condenstion. Needless to say the rate of hydrolysisand rate of condensation is dependent on the nature of the silaneitself. Some silanes quickly hydrolyze in neutral solutions while othershydrolyze so slowly that hydrolysis must be performed at a low pH forextended periods of time. Some silanes condense almost immediately ineven slightly basic solutions while others remain stable for longperiods of time even at high pH.

[0042] Before turning to details of the present invention, it should beappreciated that the present invention provides for a general method forusing silane solutions for treating anodized and unanodized magnesiumsurfaces. The exact post-treatment properties of a treated surface andthe exact conditions used to prepare a silane solution of the presentinvention are highly dependent on the nature of a specific silane used.In addition, the present invention provides five specific silanesolutions for treating magnesium surfaces. As is discussed hereinbelow,the exact composition of a solution of the present invention as well asthe method of preparation is quite flexible.

[0043] The five specific silane solutions of the present invention mayall be used alone or may be used to treat a pre-treated surface. Bypre-treated is meant, for example, treated by the aqueous hydrogenfluoride containing solution of the present invention. The aqueoushydrogen fluoride solution of the present invention is useful forconditioning a metal surface before treatment with a silane solution ofthe present invention or as a stand-alone corrosion inhibitingtreatment.

[0044] First Solution: Treatment with Hydrogen Fluoride/NonionicSurfactant Solution

[0045] The first solution of the present invention is an aqueoushydrogen fluoride (HF)/surfactant solution. A metal surface treated witha first solution of the present invention is seen to be remarkablycorrosion resistant.

[0046] It is important to note that in the art the use of HF to treatmagnesium surfaces, forming a corrosion-resistant Mg—F layer, is wellknown. Further, the use of long-chain hydrocarbon nonionic surfactantssuch as Brij® 97 on phosphate coatings of metals has been described (seeSankara Narayanan, T. S. N.; Subbaiyan, M. Metal Finishing 1993, 91,p.43 and Nair, U. B.; Subbaiyan, M. Plating and Surface Finishing 1993,80, p.66).

[0047] Composition of the First Solution of the Present Invention

[0048] The first solution of the present invention is substantially anaqueous solution of hydogen fluoride (HF), where the HF content ispreferably between 5% and 40%, even more preferably between 10% and 30%by volume to which is added a nonionic surfactant. The preferrednonionic surfactant is a polyoxyalkylene ether, preferably apolyoxyethylene ether, more preferably one of: polyoxyethylene oleylether, polyoxyethylene cetyl ether, polyoxyethylene stearyl ether,polyoxyethylene dodecyl ether, and most preferably polyoxyethylene(10)oleyl ether (sold commercially as Brij® 97). The amount of Brij® 97added is preferably 20 to 1000 ppm, more preferably 40 to 500 ppm andeven more preferably 100 to 400 ppm. When a surfactant other than Brij®97 is added, an equivalent molar amount to that stated for Brij® 97 ispreferred.

[0049] Use of the First Solution of the Present Invention

[0050] The first embodiment of the present invention involves the use ofa first solution of the present invention to treat a metal or metalalloy surface The first solution is exceptionally useful for thetreatment of bare surfaces and surfaces formed by a die casting process,especially magnesium surfaces. The first solution of the presentinvention can also be used to treat a corroded surface, simultaneouslyremoving corrosion and modifying the surface so as to improve resistanceto future corrosion. Further, it is also a preferred surfaceconditioning solution preceding treatment with a silane solution of thepresent invention.

[0051] The first embodiment of the method of the present inventioninvolves applying a first solution of the present invention to thesurface to be treated, preferably by dipping, preferably at atemperature between about 0° C. and about 40° C., more preferablybetween about 10° C. and about 30° C.

[0052] When the first solution of the present invention is applied by bydipping, the workpiece is allowed to remain exposed to the firstsolution for at least 10 minutes, preferably more than 20 minutes. Afterremoval from the first solution, excess solution is washed away.

[0053] Silane Solutions for the Treatment of Magnesium Surfaces

[0054] As discussed hereinabove, the use of silane solutions to treatmagnesium surfaces is difficult as conditions, methods of preparationand silanes must be found that bridge the opposing need of the magnesiumsurface for basic solutions with the need of silane solution to beacidic.

[0055] Most generally, the present invention is of the preparation anduse of a water/organic solution with a pH greater than 6 havinghydrolyzed silane moieties therein. When a silane solution of thepresent invention is formulated, the following factors must beconsidered.

[0056] To be suitable for use according to the present invention asilane must have at least one hydrolyzable functional group. Inapplications where it is desired to also adhese to polymer layers (e.g.to paint a treated surface) it is desirable that the silane have atleast one non-hydrolyzable functional group. The organofunctional groupsthat are suitable include amino, vinyl, ureido, epoxy, mercapto,isocyanato, methacrylato, sulfane and vinylbenzene.

[0057] a. Concentration of Silane

[0058] In general the concentration of silane in a silane solution ofthe present invention is between about 0.1% and about 30% by volume.Generally speaking, high concentrations of silane are better as a densercoating is produced. However, higher concentrations of silane also leadto a much higher rate of silane condensation and the concomitantlyhigher operating costs due to wastage of the expensive silanes. Further,as many silanes are not very soluble in water or water/organicsolutions, solutions having large proportions of silane are nothomogenous. Although the exact amounts of silane to be used aredependent on many factors, it has been found that generally it ispreferable to use a solution having between 0.5% and 20% silane byvolume, and more preferable to use a solution having between 1% and 5%silane by volume.

[0059] b. Hydrolysis

[0060] As stated above, it is of the utmost importance that a silane behydrolyzed for use in the present invention. Depending on thecomposition of the final solution, the nature of the individual silaneand the time between preparation and first use it may or may not benecessary to perform a separate hydrolysis step. Although some silaneshydrolyze very quickly even in basic solutions and whereas in some casesthe time between preparation and first use of a solution is very long,more often than not it is necessary to hydrolyze a silane in a separatestep. Hydrolysis is retarded by significant concentrations of organicsolvents and is accelerated by an acidic pH. Thus, a hydrolysis step ispreferably performed in an acidic aqueous solution as a separate step.

[0061] If a silane needs to be hydrolyzed in a separate step in anacidic solution, any acid may be used, although organic acids arepreferred. Most preferred is acetic acid as the salts of acetic acid aresoluble in the solutions of the present invention.

[0062] A generally useful method of silane hydrolysis is performed bymixing 5 parts silane with between about 4 and 10 parts water and 1 partglacial acetic acid. The time required for hydrolysis is dependent onthe silane. Typically, after 3 to 4 hours a sufficient proportion ofsilane has been hydrolyzed to allow preparation of a solution of thepresent invention.

[0063] c. Solvent

[0064] The ratio of water to organic in the solution is not per sedeterminative of the quality of the silane layer formed on the treatedmetal surface. Rather, the water/organic ratio defines the physicalproperties of the solution. In general, a high water-content is cheaper,environmentally friendly and allows for faster hydrolyzation of silanes.However, a high water-content promotes silane condensation, is lesseffective in solvating non-hydrolyzed silanes and it is difficult to drya workpiece treated using an organic-less solution. In contrast, a highorganic content retards both hydrolyzation and condensation, driesquickly and solvates silanes effectively.

[0065] Thus a desirable ratio of water to organic solvent is dependenton many factors. It is important to note, however, that the exact ratiois not of critical importance. In any case, hydrolysis of hydrolyzablesilanes releases alcohols into the silane solution, whereas a hydrolysisstep, a surface treatment step, and drag-in by treated workpieces (videinfra) releases water into the silane solution.

[0066] d. Alcohol and Other Organic Solvents

[0067] In general, any organic solvent that is miscible with water canbe used in formulating a silane solution of the present invention.Although generally when methanol is used in formulating a silanesolution of the present invention the best coating results are achieved,the difference is minor enough that the specific organic solvent chosenis not very important. Adequate coating results are achieved using manytypes of alcohol, especially lower aliphatic alcohols such as methanol,ethanol, propanol, isopropanol, butanol isomers and pentanol isomers.Adequate coating results are also achieved using non-alcohol organicsolvents such as acetone, diethyl ether and ethyl acetate. Mixtures ofindividual organic solvents are also effective. Selection of a specificorganic solvent or mixture of organic solvents is dependent on factorssuch as price, waste disposal, toxicity, safety, environmentfriendliness, rate of evaporation and solubility. However it is clear toone skilled in the art that due to solubility considerations coupledwith property of an organic solvent to reduce the rate of silanecondensation, the optimal choice of organic solvent may be dependent onthe nature of the silane used.

[0068] e. Preparation

[0069] In general a first step of preparing a solution of the presentinvention is dependent on the silane used. If it is necessary that thesilane be hydrolyzed in a separate step, this is done.

[0070] If no separate hydrolysis step is necessary the silane isdirectly diluted in the water/organic solution. Otherwise, after asufficient time, the silane hydrolysis solution is diluted in thewater/organic solution.

[0071] In some cases the diluted solution is not homogenous and cloudy,indicative that unhydrolyzed silane is not completely dissolved.Although a not homogenous solution can be used to treat a surface,adjusting the pH (see immediately hereinbelow) or addition of organicsolvent may solublize the remaining not hydrolyzed silane. It isimportant to note that many silanes hydrolyze slowly in a solution ofthe present invention so that often, during use, remaining undissolvedsilane is eventually hydrolyzed even without further intervention.

[0072] f. Adjusting the pH

[0073] Before use, the pH of the silane solution of the presentinvention must be adjusted to a desired value. According to the presentinvention, in order to treat an unanodized magnesium surface, a solutionof the present invention must have a pH above about 6, and morepreferably above about 8. If the pH is not in the desired range, the pHis preferably adjusted using an inorganic base and most preferably KOH,NaOH or NH₄OH.

[0074] According to the present invention, for treating an anodizedmetal surface, the pH of a silane solution must be greater than about 4,vide infra.

[0075] g. Buffers

[0076] Both for hydrolysis and for the silane solution itself, it isoften advantageous to use a pH buffer. The use of a pH buffer may beuseful for industrial process control, especially under goodmanufacturing practice (GMP) discipline or to ensure the stability of aspecific silane. The preferred buffer systems are those which do notproduce precipitate in the solutions used. Most preferred are buffersystems using ammonium acetate or sodium acetate.

[0077] h. Surfactants

[0078] In many cases it may be advantageous to add nonionic surfactantsto a silane solution of the present invention to increase corrosionresistance of a treated surface. The preferred surfactants as well asthe amounts added are as listed hereinabove for the first solution ofthe present invention.

[0079] i. Pretreatment

[0080] Before treating a metal surface with a solution of the presentinvention, it is advantageous to pre-treat the surface to increasecorrosion resistance even beyond the remarkable corrosion resistancegained from using the silane solutions of the present invention alone.Pre-treatment can be performed, for example, by treating with HF as isknown in the art or with a fluoride/phosphate solution as described, forexample, in U.S. Pat. No. 5,683,522. Best results, however, are obtainedby pre-treatment using the first solution of the present invention.

[0081] i. Application

[0082] Treatment of a metal surface using a silane solution of thepresent invention is preferably done by dipping, spraying, wiping orbrushing.

[0083] When the silane solution of the present invention is applied tothe magnesium surface by dipping, the workpiece is preferably exposed tothe silane solution for at least 1 minute, although even a few secondsis often enough. After removal from the solution, the workpiece is drip,blow or air-dried.

[0084] When a silane solution of the present invention is applied to amagnesium surface by spraying, at least about 0.1 ml solution/cm² ofmetal surface to be treated is sprayed. Thereafter, the workpiece isdrip, blow or air-dried.

[0085] The temperature of the solution during application is notcritical so there is no need to heat the solution. Since heatingrequires an additional energy expenditure and may lead to an increasedrate of silane condensation, application preferably occurs at ambienttemperatures that is preferably at a temperature between about 0° C. andabout 40° C., more preferably between about 10° C. and about 25° C.

[0086] j. Curing

[0087] As is clear to one skilled in the art, a silane layer cured atelevated temperatures (e.g. preferably above about 110° C.) converts toa siloxane layer. It has been found that all things being equal, asurface treated with a silane solution of the present invention andsubsequently cured has a greater corrosion resistance but lowered paintadhesion than a treated but not cured surface.

[0088] Curing can be performed for virtually any length of time, fromhalf a minute up to even hours.

[0089] k. Storage of a Silane Solution

[0090] As is clear to one skilled in the art, in an industrial settingwhere a silane solution of the present invention is applied by dippingthe workpiece into a bath of the solution, the solution is rarely madeanew for every workpiece. Rather a bath is filled with a preparedsolution and the contents therein are periodically replenished. Thus,when formulating a silane solution of the present invention for such anapplication this must be kept in mind. In general, for long-term storagethe silane concentration and pH of a solution of the present inventionmust be chosen so that silane condensation is minimized. The primary“contaminant” that may enter the bath is water dragged-in by workpieces.Although water drag-in does not change the pH, it may increase theproportion of water to a point that silane condensation occurs quickly

[0091] Additionally, the slow rate of silane hydrolysis at the pH of asilane solution of the present invention must be taken into account.Even if a specific silane hydrolyzes only slowly, the rate may besufficient so that no special action needs be taken. Pure silane isadded (taking care that the final silane concentration in the bath doesnot exceed the desired) and slowly hydrolyzes. When a silane is usedthat cannot hydrolyze efficiently at the pH of the silane solution, theadded silane is first hydrolyzed in a separate step and then added tothe silane solution.

[0092] It is clear to one skilled in the art that in applications wherea solution of the present invention is to be stored or kept for anextended period of time, it is often advantageous to use a pH buffer, asdescribed hereinabove. Further, it is also clear to one skilled in theart that the composition of a silane solution of the present inventionis not sharply defined but rather can change with time.

[0093] Specific Silane Solutions of the Present Invention

[0094] Second Solution: Bis-triethoxysilylpropyl Tetrasulfane Solution

[0095] The second solution of the present invention is abis-triethoxysilylpropyl tetrasulfane solution. Abis-triethoxysilylpropyl tetrasulfane solution of the present inventionis exceptionally useful for the treatment of bare magnesium surfaces ora magnesium surface pretreated using the first solution of the presentinvention. The silane layer formed allows excellent powder-paint orE-coating adhesion but also acts as an excellent corrosion resistant andwater repellant protective coating. The water repellance is so greatthat when liquid paint is applied, the paint beads on a treated surface.A bis-triethoxysilylpropyl tetrasulfane solution of the presentinvention is also exceptionally useful for the treatment of anodizedsurfaces, see below.

[0096] Due to the slow rate of hydrolysis, bis-triethoxysilylpropyltetrasulfane is preferably hydrolyzed in a separate step beforeformulation of the silane solution of the present invention itself.Hydrolysis is preferably performed as described hereinabove, for between3 and 12 hours. Even after such a long hydrolysis time, the resultingsolution is cloudy, indicative that a significant proportion of thebis-triethoxysilylpropyl tetrasulfane is neither hydrolyzed nordissolved.

[0097] After hydrolysis, the bis-triethoxysilylpropyl tetrasulfanesolution of the present invention is ideally made-up with awater/organic solution having between about 70% and about 100% organicsolvent, more preferably between about 90% and about 100% organicsolvent. It has been observed that even in solutions with only moderatewater content, at useful pHs the bis-triethoxysilylpropyl tetrasulfanequickly undergoes condensation.

[0098] The second solution of the present invention preferably has a pHabove about 6, more preferably between about 6 and about 10, and mostpreferably between about 7 and about 8.

[0099] Third Solution: Vinyl Silane Solution

[0100] The third solution of the present invention is a vinyl silanesolution. Of the four substituents of the silicon atom in the silane, atleast one is a hydrolyzable moiety (preferably an alkoxy moiety such asmethoxy or ethoxy or an aryloxy or acyloxy moiety) and at least one is avinyl moiety. For example, vinyltrimethoxysilane is an ideal silane foruse in formulating the third solution of the present invention.

[0101] As described hereinabove the purpose of the hydrolyzable moietyis to allow silane binding to the metal surface whereas the purpose ofthe vinyl moiety is to interact with a following paint layer. Thus, athird vinyl silane solution of the present invention is exceptionallyuseful for the treatment of bare surfaces or a surface treated using thefirst solution of the present invention. The silane layer formed allowsexcellent liquid-paint (especially epoxy paint systems, acrylic paintsystems and polyurethane paint systems) adhesion but also acts as astand-alone corrosion resistant coating.

[0102] Due to the slow rate of hydrolysis in high pH, vinyl silanes suchas vinyltrimethoxysilane are preferably hydrolyzed in a separate stepbefore formulation of the silane solution of the present inventionitself. Hydrolysis is preferably performed as described hereinabove.

[0103] After hydrolysis, the vinyl silane solution of the presentinvention is ideally made up with a water/organic solution havingbetween about 25% and about 75% organic solvent, more preferably betweenabout 40% and about 60% organic solvent.

[0104] The vinyl silane solution of the present invention preferably hasa pH above about 6, more preferably between about 7 and about 10, andmost preferably between about 6 and about 7.

[0105] Fourth Solution: Amino Silane Solution

[0106] The fourth solution of the present invention is an amino silanesolution. Of the four substituents of the silicon atom in the silane, atleast one is a hydrolyzable moiety (preferably an alkoxy moiety such asmethoxy or ethoxy or an aryloxy or acyloxy moiety) and at least one isan amino moiety. For example, aminotrimethoxysilane is an ideal silanefor use in formulating the fourth solution of the present invention.

[0107] As described hereinabove the purpose of the hydrolyzable moietyis to allow silane binding to the metal surface whereas the purpose ofthe amino moiety is to interact with a subsequent paint layer. Thus, afourth amino silane solution of the present invention is useful for thetreatment of bare (recently cleaned) surfaces or a surface treated usingthe first solution of the present invention. The amino silane layerformed allows good liquid-paint (especially epoxy paint systems, acrylicpaint systems and polyurethane paint systems) adhesion but also acts asa corrosion resistant coating. That said, it has been found that thecorrosion resistance of a surface treated with a fourth solution of thepresent invention is inferior to that afforded by other solutions of thepresent invention. However, the ease of preparation (see immediatelyhereinbelow) of the fourth solution of the present invention is suchthat the fourth solution of the present invention can be used in aneffective fashion to temporarily protect magnesium workpieces in thestead of oils or greases.

[0108] Amino silanes are resistant to condensation and have a naturallybasic pH. Thus when preparing a fourth solution of the present inventionit is usually possible to omit the step of addition of base. Further,amino silanes hydrolyze very quickly even in basic solutions. It istherefore not necessary to perform a separate hydrolysis step when usingamino silanes according to the present invention. Hydrolysis is in factso quick that, for example, a 5% solution of aminotrimethoxysilane inwater can be made and directly applied (for example by spraying) to amagnesium surface of a workpiece.

[0109] Fifth Solution: Ureido Silane Solution

[0110] The fifth solution of the present invention is a ureido silanesolution. Of the four substituents of the silicon atom in the silane, atleast one is a hydrolyzable moiety (preferably an alkoxy moiety such asmethoxy or ethoxy or an aryloxy or acyloxy) and at least one is anureido moiety. For example, ureidopropyltrimethoxysilane is an idealsilane for preparing the fifth solution of the present invention.

[0111] As described hereinabove the purpose of the hydrolyzable moietyis to allow silane binding to the metal surface whereas the purpose ofthe ureido moiety is to interact with a subsequent paint layer. Thus, afifth ureido silane solution of the present invention is exceptionallyuseful for the treatment of bare surfaces or a surface treated using thefirst solution of the present invention. The silane layer formed allowsexcellent liquid-paint (especially epoxy paint systems, acrylic paintsystems and polyurethane paint systems) adhesion but also acts as astand alone corrosion resistant coating.

[0112] Ureido silanes are resistant to condensation and have a naturallybasic pH. Thus it is usually possible to omit the step of addition ofbase when formulating a ureido silane solution of the present invention.Further, ureido silanes hydrolyse very quickly even in basic solutions.It is therefore not necessary to perform a separate hydrolysis step whenusing ureido silanes according to the present invention. That said, itis often preferable to first add a ureido silane to an equal volume ofwater and, after between 15 and 30 minutes, to dilute thethus-hydrolyzed silane with a water/organic solvent.

[0113] The ureido silane solution of the present invention preferablyhas a pH above about 6, more preferably above about 8 and mostpreferably above about 10.

[0114] Treatment of Anodized Magnesium Surfaces

[0115] Unlike unanodized magnesium surfaces, anodized magensium surfaceshave a sufficient hydroxy concentration for effective silane bindingeven at an acidic pH. Further, anodized surfaces are acid-resistant socan be treated at the lower pHs which are more suitable for silanesolutions,

[0116] It is important to note that when a silane solution of thepresent invention is used to treat an anodized surface, the anodizationmust be performed in a basic and not in acidic solution. It has beenfound that silanes do not effectively bind to surfaces anodized underacidic conditions. Examples of anodizing processes performed in a basicsolution are described in U.S. Pat. No. 4,978,432 and U.S. Pat. No.5,264,113.

[0117] Second Solution: Bis-triethoxysilylpropyl Tetrasulfane Solution

[0118] As stated hereinabove, the second solution of the presentinvention, a bis-triethoxysilylpropyl tetrasulfane solution, isexceptionally useful in treating anodized surfaces. The silane layerformed allows excellent powder-paint or E-coating adhesion but also actsalones as an excellent corrosion resistant and water-repellantprotective coating.

[0119] When the second solution is used to treat an anodized surface,the pH is preferably close to neutral, in the range of from about 5 toabout 8 and more preferably from about 6 to about 7.

[0120] When used to treat an anodized surface, the amount ofbis-triethoxysilylpropyl tetrasulfane used is preferably from about 0.1%to about 5% of the solution, more preferably from about 0.8% to about2%, and most preferably from about 1% to about 2%.

[0121] Sixth Solution: Vinyl Silane with a Nonfunctional BisilylSolution

[0122] The sixth solution of the present invention is composed of amixture of two silanes, a vinyl silane and a nonfunctional bisilylcompound

[0123] The nonfunctional bisilyl compound used in formulating the sixthsolution of the present invention is preferably a nonfunctional bisilylalkyl compound such as 1,2 bis-(triethoxysilyl) ethane. Other preferrednonfunctional bisilyl compounds include 1,2-bis-(trimethoxysilyl)ethane, 1,6-bis-(trialkoxysilyl) hexanes and 1,2-bis-(triethoxysilyl)ethylene.

[0124] Nonfunctional bisilyl compounds tend to condense very quickly ata basic pH so are unsuitable for use in sealing unanodized magnesiumsurfaces as described hereinabove. However, it has been found thatnonfunctional bisilyl compounds lend remarkable corrosion resistance toanodized surfaces when used in accordance with the teachings of thepresent invention.

[0125] The lack of a non-hydrolyzable moiety on these nonfunctionalbisilyls prevents painting of an anodized surface after treatmentexclusively with a nonfunctional bisilyl. To overcome this disadvantage,a vinyl silane is also used when formulating the sixth solution of thepresent invention. As described above for the third solution of thepresent invention, of the four substituents of the silicon atom in thevinyl silane, at least one is a hydrolyzable moiety (preferably analkoxy moiety such as methoxy or ethoxy or an aryloxy or acyloxy moiety)and at least one is a vinyl moiety. For example, vinyltrimethoxysilaneis an ideal silane for use in formulating the sixth solution of thepresent invention. As described hereinabove the purpose of thehydrolyzable moiety is to allow silane binding to the metal surfacewhereas the purpose of the vinyl moiety is to interact with a subsequentpaint layer.

[0126] A sixth silane solution of the present invention is exceptionallyuseful for the treatment of anodized surfaces or an anodized surfacetreated using the first solution of the present invention. The silanelayer formed allows excellent liquid-paint (especially epoxy paintsystems, acrylic paint systems and polyurethane paint systems) adhesion,an excellent E-coating pretreatment and also acts as a stand-alonesealing and protective coating for anodized surfaces.

[0127] When formulating a sixth solution of the present invention, thetotal amount of silane is preferably between about 0.1% and about 30%,more preferably between about 0.5% and about 20%, and even morepreferably between about 1% and about 5% silane by volume. Any ratio ofsilanes can be used, but preferably the molar ratio of nonfunctionalbisilyl to vinyl silyl is between about 50:50 to about 10:90, morepreferably the ratio is between about 20:80 and about 10:90. It isimportant to note that the ratios stated herein refer to the ratio ofsilanes added to the solution, and not to the ratio of hydrolyzedsilanes in the solution when ready for use.

[0128] Hydrolysis is preferably performed as described hereinabove,wherein first the two silanes are combined and thereafter hydrolyzed inan aqueous acid solution

[0129] After hydrolysis, the sixth silane solution of the presentinvention is ideally made up with a water/organic solution havingbetween about 25% and about 75% organic solvent, more preferably betweenabout 40% and about 60% organic solvent.

[0130] The sixth solution of the present invention preferably has a pHbetween about 4 and about 7, and more preferably between about 4 andabout 5.

SPECIFIC SYNTHETIC EXAMPLES

[0131] First Solution of the Present Invention

[0132] 70% HF was diluted with distilled water to make a 20% HFsolution. To the 20% HF solution 300 ppm Brij® 97 was added. Thesolution was labeled solution A.

[0133] Corrosion Resistance After Treatment with a First Solution of theInvention

[0134] Two solid magnesium diecast blocks were cleaned in a strongalkaline cleaning solution, rinsed in excess water. One block was dippedfor 25 minutes in a 20% HF solution while the other block was dipped for25 minutes in a bath of solution A. The two blocks were allowed to airdry.

[0135] The blocks were exposed to 5% salt fog in accordance withrequirements of the ASTM-117. After 8 hours, corrosion was observed onthe block exposed to solution A, compared to only six hours for theblock exposed to the HF solution.

[0136] Corrosion Resistance of a Corroded Surface After Treatment with aFirst Solution of the Invention

[0137] A solid magnesium diecast corroded block was dipped in a bathcontaining solution A for 25 minutes. The block was allowed to air dry.

[0138] The corroded block was exposed to 5% salt fog in accordance withrequirements of the ASTM-117. After 8 hours, the diecast block retainedits original, albeit corroded, appearance.

[0139] Second Solution of the Present Invention

[0140] Corrosion Resistance After Treatment with a Second Solution ofthe Invention

[0141] 5 ml of glacial acetic acid were added to 50 ml of water. To thisacid solution was added 50 ml bis-triethoxysilylpropyl tetrasulfane. Thesilane/acetic acid solution was stirred for three hours to allow silanehydrolyzation. After the three hours, the silane/acetic acid solutionwas added to a 4:1 mixture of ethanol and isopropanol to get one literof solution B1, a second solution of the present invention. The pH ofsolution B1 was adjusted to approximately 7.5 by addition of a 1 M NaOHsolution.

[0142] A solid magnesium diecast block and a Thixomold® block of AZ91alloy were cleaned in a strong alkaline cleaning solution, rinsed inexcess water and dipped in a bath containing solution B1 for 2 minutes.The two blocks were allowed to air dry.

[0143] The electrical resistance of the two blocks was tested inaccordance with Fed. Std. No. 141. The electrical resistance of bothblocks was 0.004 Ohm/inch².

[0144] The diecast block was exposed to 5% salt fog in accordance withrequirements of the ASTM-117. After 48 hours, the diecast block retainedits original appearance. A control block of a chromate conversiontreated magnesium block was heavily corroded under the same conditions.

[0145] The Thixomold® block was immersed in a 5% solution of sodiumchloride. After 24 hours only minimal pitting was observed. A controlblock of a chromate conversion treated Thixomold® block was heavilycorroded under the same conditions.

[0146] Corrosion Resistance of Anodized Part After Treatment with aSecond Solution of the Invention

[0147] Two diecast blocks of Az91 alloy were anodized with a 12 micronlayer using the basic pH anodizing procedures described in MIL-M-45202Type II. One of the two blocks was immersed in a bath containingsolution B1 for 2 minutes. The block was allowed to air dry. Both blockswere exposed to 5% salt fog in accordance with requirements of theASTM-117. The first corrosion pits were observed after 300 hours in theuntreated block. The first corrosion pits were observed after 500 hoursin the block treated with solution B1.

[0148] Powder Paint Adhesion After Treatment with a Second Solution ofthe Invention

[0149] 2.5 ml of glacial acetic acid were added to 25 ml of water. Tothe acid solution was added 25 ml bis-triethoxysilylpropyl tetrasulfane.The silane/acetic acid solution was stirred for three hours to allowsilane hydrolyzation. After the three hours, the silane/acetic acidsolution was added to a 4:1 mixture of ethanol and isopropanol to getone liter of solution B2, a second solution of the present invention.The pH of solution B2 was adjusted to approximately 7.5 by addition of a1 M NaOH solution.

[0150] A diecast block of Az91 alloy were cleaned in a strong alkalinecleaning solution, rinsed in excess water and dipped in a bathcontaining solution B2 for 2 minutes. The block was allowed to air dry.After drying the block was painted using an epoxy-phenolic powdercoating system.

[0151] The adhesion of the paint to the block treated with solution B2was tested in accordance with requirements of DIN ISO 2409. The partpassed the test. A control block was painted in an identical fashionafter only a cleaning, rinsing and drying step. The paint peeled fromthe control block under the test conditions.

[0152] Powder Paint Resistance to Corrosion After Treatment with aSecond Solution of the Invention

[0153] Three diecast blocks of AZ91 alloy were cleaned in a strongalkaline cleaning solution and rinsed in excess water. The second andthird blocks were both dipped in a bath containing solution B2 for 2minutes. The blocks were allowed to air dry. After drying, the first(untreated) and third (treated) block were painted using anepoxy-phenolic powder coating system.

[0154] Adhesion of the paint to the first (untreated) block was so poorthat the block was not tested further.

[0155] The second and third diecast blocks were exposed to 5% salt fogin accordance with requirements of the ASTM-117. After 48 hours, thefirst signs of corrosion were observed on the second (unpainted) block

[0156] The third diecast block that was treated and painted showed noevidence of corrosion, even after 1000 hours of exposure to the saltfog.

[0157] First, Third, Fourth and Fifth Solutions of the Present Invention

[0158] 25 2.5 ml of glacial acetic acid were added to 25 ml ofvinyltrimethoxysilane. To the acid/silane solution was added 25 mlwater. The silane/acetic acid solution was stirred for three hours toallow silane hydrolyzation. After the three hours, the silane/aceticacid solution was added to a 4:1:5 mixture of ethanol/isopropanol/waterto get one liter of solution C1, a third solution of the presentinvention. The pH of solution C1 was adjusted to approximately 6.5 byaddition of a 1 M sodium hydroxide solution.

[0159] In a similar fashion a fourth solution of the present inventionC2 was made having 25 ml of aminotrimethoxysilane. Sinceaminotrimethoxysilane hydrolyzes quickly, it was diluted, withoutadditional acid, in 975 ml of a 4:1:5 mixture ofethanol/isopropanol/water.

[0160] In a similar fashion a fifth solution of the present invention C3was made having 25 ml of ureidotrimethoxysilane. Sinceureidotrimethoxysilane hydrolyzes quickly, it was diluted, withoutadditional acid, in 975 ml of a 4:1:5 mixture ofethanol/isopropanol/water.

[0161] Corrosion Resistance After Treatment with Third, Fourth and FifthSolutions of the Invention

[0162] Three diecast blocks made of magnesium AM-60 were cleaned in astrong alkaline cleaning solution and rinsed with water.

[0163] The first block was immersed in solution C1 for 2 minutes andblow-dried. The second block was immersed in solution C2 for 2 minutesand blow-dried. The third block was immersed in solution C3 for 2minutes and blow-dried.

[0164] The three blocks were exposed to 5% salt fog in accordance withrequirements of the ASTM-117. More than 1% corrosion appeared on thefirst block after 24 hours. At least 1% corrosion appeared on the secondblock after 8 hours. At least 1% corrosion appeared on the third blockafter 16 hours.

[0165] Corrosion Resistance After Treatment with a First and ThirdSolution of the Invention

[0166] Three diecast blocks made of magnesium AM-60 were cleaned in astrong alkaline cleaning solution and rinsed with water.

[0167] A first block was dried.

[0168] The second and third block were immersed in solution A for 25minutes and subsequently rinsed with water.

[0169] The second block was dried.

[0170] The third block was immersed in solution C1 for 2 minutes andthereafter cured in an oven at a temperature of 120° C.

[0171] The three blocks were exposed to 5% salt fog in accordance withrequirements of the ASTM-117. More than 1% corrosion appeared on thefirst block after 1 hour. At least 1% corrosion appeared on the secondblock after 8 hours. At least 1% corrosion appeared on the third blockafter 24 hours.

[0172] Wet Paint Adhesion After Treatment with a Third Solution of theInvention

[0173] A diecast block of AM-60 alloy were cleaned in a strong alkalinecleaning solution, rinsed in excess water and dipped in a bathcontaining solution C1 for 2 minutes. The block was allowed to air dry.After drying the block was painted using a polyurethane paint system.

[0174] The adhesion of the paint to the block treated with solution C1was tested in accordance with requirements of DIN ISO 2409. The blockpassed the test.

[0175] Surface Residue After Treatment with a First and Third Solutionof the Invention

[0176] A die-cast block of AZ-91 alloy was treated successively withsolution A and solution C. After treatment with solution A,spectrophotoscopic analysis of the surface showed the following surfaceatomic concentrations (in percent): S C Ca N O F Na Mg Al Si 1.4 31.14.1 1.3 18.9 12.2 1.4 27 2.7 —

[0177] After treatment with solution C, spectrophotoscopic analysis ofthe surface showed the following surface atomic concentrations (inpercent): S C Ca N O F Na Mg Al Si — 26.0 — — 44.1 2.6 — 3.9 0.1 23.4

[0178] From the evidence it is seen that solution A produces afluorine-rich layer on the surface of the AZ-91 block and that solutionC left a silane-rich layer on the surface on top of the fluorine-richlayer.

[0179] After 17 minutes of sputter cleaning (at 10 A/min), the atomicconcentration of Si at the surface decreased from 19.64% to 19.31%.Under the same conditions the atomic concentration of magnesiumincreased from 1.71 to 15.0% and of fluorine from 4.86% to 16.99%. Notethat the differences in starting concentrations found in the sputtercleaning and the spectrophotoscopic analyses are attributable todifferent cleaning procedures used in these two different analyses.

[0180] Thus successive treatment of a magnesium block using a firstsolution of the present invention and a silane-containing solution ofthe present invention produces a magnesium magnesium fluoride:silane“sandwich”.

[0181] Sixth Solution of the Present Invention

[0182] Corrosion Resistance After Treatment with a Sixth Solution of theInvention

[0183] 5 ml of glacial acetic acid were added to a mixture of 40 mlvinyltrimethoxysilane and 10 ml of bis-triethoxysilyl ethane. To thesilane/acid solution was added 50 ml water. The silane/acetic acid/watersolution was stirred for six hours to allow silane hydrolyzation. Afterthe six hours, the silane/acetic acid solution was added to a 4:1:5mixture of ethanol/isopropanol/water to get one liter of solution D, asixth solution of the present invention. The pH of solution D wasadjusted to approximately 4.5 by addition of a 1 M NaOH solution.

[0184] Two diecast blocks of magnesium alloy AM-60 alloy were anodizedwith a 12-micron layer using the basic pH anodizing procedures known inthe art as ANOMAG®. One of the two blocks was immersed in a bathcontaining solution D for 2 minutes. The blocks were allowed to air dry.

[0185] Both blocks were exposed to 5% salt fog in accordance withrequirements of the ASTM-117. The first corrosion pits were observedafter 48 hours in the untreated block. The first corrosion pits wereobserved after 260 hours in the block treated with solution D.

[0186] Wet Paint Adhesion After Treatment with a Sixth Solution of theInvention

[0187] A diecast blocks of magnesium alloy AM-60 alloy was anodized witha 12 micron layer using the anodizing procedure described in U.S.provisional patent No. 60/301,147 and in a copending patent applicationby the same inventor. The block was immersed in a bath containingsolution D for 2 minutes. The block was allowed to air dry. After dryingthe block was painted using a polyurethane paint system.

[0188] The adhesion of the paint to the block treated with solution Dwas tested in accordance with requirements of DIN ISO 2409. The blockpassed the test. A control block was painted in an identical fashionafter only a cleaning, rinsing and drying step. The paint peeled fromthe control block under the test conditions.

1. A method of treating a workpiece comprising: a) providing a surface of the workpiece, said surface chosen from the group consisting of magnesium surfaces and magnesium alloy surfaces; b) contacting said surface with a strong alkaline cleaning solution and then rinsing the cleaned surface of the workpiece with water; c) preparing a treatment solution having a pH greater than about 4 and containing a non-water water miscible solvent and at least one hydrolyzable silane that is at least partially hydrolyzed in a solvent; and d) contacting said surface with said treatment solution.
 2. The method of claim 1 wherein said solvent comprises at least one of the substances chosen from a group consisting of water, alcohols, acetone, ethers and ethyl acetate.
 3. The method of claim 1 wherein at least one of said at least one hydrolyzable silane has at least one functional group from a group consisting of amino, vinyl, ureido, epoxy, mercapto, isocyanato, methacrylato, vinylbenzene and sulfane.
 4. The method of claim 1 wherein at least one of said at least one hydrolyzable silane is chosen from a group consisting of bis-triethoxysilylpropyl tetrasulfane, vinyltrimethoxysilane, aminotrimethoxysilane, and ureidopropyltrimethoxysilane.
 5. The method of claim 1 wherein said treatment solution has a pH greater than about 6, preferable greater than about
 8. 6. The method of claim 1 wherein said preparing a treatment solution comprises: i. preparing a hydrolyzing solution by mixing a hydrolyzable silane in an aqueous solution; and ii. subsequent to said mixing ensuring that said hydrolyzing solution has a pH of less than about
 6. 7. The method of claim 6 wherein said ensuring that said hydrolyzing solution has a pH of less than about 6 comprises adding an amount of acid to said hydrolyzing solution.
 8. The method of claim 7 wherein said acid is acetic acid.
 9. The method of claim 1 wherein said preparing a treatment solution comprises: i. mixing an amount of said at least one hydrolyzable silane with said solvent; and ii. ensuring that said treatment solution has a desired pH.
 10. The method of claim 9 wherein said ensuring that said treatment solution has a desired pH comprises adding an amount of a base to said treatment solution.
 11. The method of claim 10 wherein said base is chosen from a group consisting of KOH, NaOH and NH₄OH.
 12. The method of claim 9 wherein said amount of said at least one hydrolyzable silane is chosen so that a total hydrolyzable silane content of said treatment solution is between about 0.1% and about 30% by volume, preferable between about 0.5% and about 20% by volume, more preferred between about 1% and about 5% by volume.
 13. A composition useful for treating of a magnesium or magnesium alloy surface comprising: a) a non-water water-miscible solvent; and b) one hydrolyzable silane with at least one functional group consisting of sulfane; c) water; wherein a pH of the composition is greater than about
 6. 14. The composition of claim 13 wherein said pH is greater than about
 8. 15. The composition of claim 13 wherein said non-water water-miscible solvent comprises at least one of the materials chosen from a group consisting of water, alcohols, acetone, ethers and ethyl acetate.
 16. A composition useful for treating of a magnesium or magnesium alloy surface comprising: a) a non-water water-miscible solvent; and b) one hydrolyzable silane with at least one functional group consisting of amine; c) water; wherein a pH of the composition is greater than about
 6. 17. The composition of claim 16 wherein said pH is greater than about 8, more preferable greater than about
 10. 18. The composition of claim 16 wherein said non-water water-miscible solvent comprises at least one of the materials chosen from a group consisting of water, alcohols, acetone, ethers and ethyl acetate.
 19. The composition of claim 13 wherein said hydrolyzable silane is bis-triethoxysilylpropyl tetrasulfane.
 20. The composition of claim 16 wherein said hydrolyzable silane is aminotrimethoxysilane.
 21. An anti-corrosion coating comprising: a. a layer including magnesium atoms; and b. silane moieties attached to at least some of said magnesium atoms in said layer by Si—O—Mg bonds.
 22. A method of binding silanes moieties to a magnesium or magnesium alloy surface comprising: a) providing a surface having a plurality of magnesium atoms; b) contacting said surface with a strong alkaline cleaning solution and then rinsing the cleaned surface of the workpiece with water; and d) applying to said surface a treatment solution with a pH greater than about 4, said treatment solution including at least one hydrolyzable silane wherein at least a portion of said at least one hydrolyzable silane is hydrolyzed.
 23. The method of claim 22 wherein at least one of said at least one hydrolyzable silane has at least one functional group from a group consisting of amino, vinyl, ureido, epoxy, mercapto, isocyanato, methacrylato, vinylbenzene and sulfane.
 24. The method of claim 22 wherein at least one of said at least one hydrolyzable silane is chosen from a group consisting of bis-triethoxysilylpropyl tetrasulfane, vinyltrimethoxysilane, aminotrimethoxysilane, and ureidopropyltrimethoxysilane.
 25. The method of claim 22 wherein said treatment solution has pH greater than about 6, more preferable greater than about
 8. 26. The method of claim 22 wherein said solution comprises at least one of the substances chosen from a group consisting of water, alcohols acetone, ethers and ethyl acetate.
 27. An article comprising: a. at least one magnesium-containing surface; and b. a coating, said coating including a plurality of silane moieties, said silane moieties bound to said magnesium-containing surface by Si—O—Mg bonds.
 28. The article of claim 27 wherein at least about 1% of said plurality of silane moieties has at least one functional group from a group consisting of amino, vinyl, ureido, epoxy, mercapto, isocyanato, methacrylato, vinylbenzene and sulfane. 